Answer:
2 hours
Explanation:
given that the calorie burn rates are:
swimming: 400 cal / hour
rollerblading: 600 cal / hour
If he swims for 3 hours, he will burn:
400 cal / hour x 3 hours
= 1200 cal
Since his goal is 2400 calories, the number of calories that he has left to burn after swimming is:
2400 - 1200
= 1200 calories.
Number of hours of rollerblading to burn 1200 calories
= 1200 calories ÷ 600 calories per hour
= 2 hours